Typically, a door of a vehicle is pivotally coupled to the body of the vehicle through a hinge and selectively opened and closed by being pivoted about the hinge. A door check mechanism is arranged between the door and the body and the door is held at a certain opening degree by the door check mechanism. That is, the door check mechanism has a check link pivotally coupled to the body and a door check fixed in the door, through which the check link is inserted. The door check mechanism holds the door at the certain opening degree by engaging the door check with the check link and applying resistance force to movement of the door.
For example, to hold a door at a certain opening degree, Patent Document 1 proposes that a fastening mechanism be provided that applies constraint force to movement of a check link.